The invention relates to a roof-mounted air conditioning system for motor vehicle use.
As described in an earlier application of the same assignee (U.S. patent application Ser. No. 703,991, filed Feb. 21, 1985), an air conditioning system, particularly intended for buses comprises the following: a condenser part having a large surface condenser block which is downwardly inclined and is transversely extending, relative to a forward driving direction, and a condenser blower for discharging exhaust air from the condenser. This system also comprises an evaporator part separated from the condenser part by a transversely extending part, and evaporator blocks separated from each other, in parallel, relative to a forward driving direction. The evaporator part also comprises an air intake space and an evaporator blower which distributes circulating air, drawn in by an air intake device, as cooled air to the passenger space of the vehicle, after its passage through the evaporator past.
The air conditioning system according to assignee's previous application is designed to achieve a relatively low overall height above the roof of the vehicle. To this end, the air conditioning system can be integrated into the framework of the roof. The condenser part, together with the large surface condenser block, which is downwardly inclined relative to a forward driving direction, is partially lowered at the rear section of the vehicle roof so that it extends below the roof level.
On the basis of German Offenlegungsschrift No. 32 24 895, an air conditioning unit is known which is specifically intended for roof mounting on buses. This air conditioning system has a flat construction, in which a condenser and an evaporator are arranged behind one another, relative to a forward driving direction, and are mounted on the roof, and trough-shaped elements, housing the condenser and evaporator parts, are adapted to the contour of the roof.
German Offenlegungsschrift No. 27 57 415 discloses an air conditioning system for roof mounting in which the condenser block has an upright configuration or is upwardly inclined at a steep angle, relative to a forward driving direction. However, this arrangement presents difficulties in accommodating the large heat exchanger surfaces of the condenser that are necessary for achieving relatively high cooling performances. Because the length of the condenser block is predetermined by the maximum vehicle width and an increase in the depth of the condenser block causes the rear row of pipes to contribute, proportionately, only a very small amount to the total output. As a result, the ratios of weight, price and performance of the condenser are unfavorable. The resultant increase in the condenser's resistance to air flow requires the use of blowers with higher performance to counteract such an increased resistance effect, which in turn, adds to the weight and cost of the system.
German Gebrauchsmuster No. 77 14 617 discloses yet another air conditioning system for roof mounting which has two parallel condenser blocks extending in a forward driving direction. Since the available height is limited, the heat exchanger surfaces can only be expanded by extension of their length or depth. This, in turn, necessitates relatively deep condenser blocks. Additionally, air deflection is necessary to overcome the problem of an increased air flow resistance in the condenser part.
It is a primary objective of the present invention to provide a roof-mounted air conditioning system for vehicles of the type mentioned, having a design which is more compact, smaller, flatter and lighter in weight as well as with a favorable ratio of high power density to a small structural volume.
A further object of the invention is to provide an air conditioning system which will be cost-effective for purposes of retrofit installation and maintenance purposes.
The air conditioning system of the invention meets the above objectives, in accordance with embodiments of the invention, by providing an inclined condenser block having an uppermost edge that is approximately flush with the upper edge of the evaporator block.
In accordance with an essential feature of the invention, the condenser, with the downwardly inclined condenser block, is arranged between the evaporator blocks of the evaporator part, in order to reduce the overall height and to enhance compactness of the system.
The arrangement with the uppermost edge of the evaporator block being approximately flush with the uppermost edge of the condenser block results in a nested effect. This nested arrangement of the condenser part and the evaporator part reduces the overall height of the air conditioning system as well as the entire overall volume thereof, and thereby achieves a high performance density with an overall small volume. Furthermore, the air conditioning system is designed in such a way that, independent of the performance requirements of the air conditioning system, the basic arrangement is symmetrical about a longitudinally extending line, i.e., relative to a forward driving direction of the motor vehicle. While the dimension of the condenser blocks, as well as the condenser parts, and/or the evaporator blocks or evaporator parts vary depending upon the performance requirements, the basic construction of the housing can, however, be selected to be the same for all perforamance capacities, independent of performance requirements. The only modification necessary is the complement of the condenser block, evaporator blocks and blowers. Such a design facilitates cost-effective production and even a reduction in manufacturing costs. The compact construction of the inventive air conditioning system reduces its weight as compared to conventional systems, resulting in a saving of total net weight.
A preferred feature of the invention is the manner in which a trough-shaped housing part transversely separates the condenser and the evaporator parts. This separation is designed, with a view to a favorable performance ratio, in such a way that, regardless of the compact construction and the nested arrangement of the condenser and evaporator parts, the space available at the exhaust side of the condenser part facilitates easy discharge of exhaust air by way of the condenser blower, unhampered by significant flow resistance. As a consequence, only a limited number of small size condenser blowers have to be provided in the area of the exhaust side of the condenser. Due to the fact that the condenser block is placed in an extremely flat position between the evaporator blocks, its operation is enhanced by the resulting dynamic pressure, and the trough-shaped housing part in the area of the discharge side is designed to facilitate the flow of the exhaust air.
The trough-shaped housing part, is further shaped in such a way that almost the entire area of the evaporator can be utilized for the cooling of the circulating air, which enhances admission of air to the evaporator blocks over their entire length and height with the utmost uniformity. When the length and height of the evaporator blocks are almost entirely utilized, the dimensions of the blocks can be adjusted to conform to desired performance requirements without consideration to design-dependent reductions in performance.
It has also proven advantageous to design the trough-shaped housing part so that it forms a U-shape in cross section. Such a configuration facilitates the installation and support of the inclined condenser blocks in the trough-shaped housing, while simultaneously providing a space in the area of the circulating air inlet of the condenser part, which is enables circulating air to be admitted over the entire height of evaporator block.
A preferred variation of the bottom wall of the trough-shaped housing part, i.e., that part of the housing part which extends longitudinally (parallel) to the evaporator blocks, is profiled so as to form an expanding outlet space. This bottom wall faces the circulating air inlet of the evaporator part. The bottom wall of the trough-shaped housing part defines the outlet expansion space, in the direction of the exhaust flow, in a manner for attaining minimum resistance to discharge of exhaust from the condenser part. In this manner, the exhaust can be discharged under favorable flow conditions to optimally utilize the output of the condenser block.
The bottom side of the trough-shaped housing extends into the area of the lower end of the condenser block approximately parallel to the angle of the condenser block, and at a distance from it which is adequate to facilitate the discharge of the exhaust from the condenser block. At the same time, this configuration of the bottom wall of the trough-shaped housing part in the area of the condenser block's lower end is chosen in such a manner that circulating air is admitted along the entire length of the evaporator blocks.
The bottom side of the trough-shaped housing is profiled so that when sectioned longitudinally, it defines an approximately trapezoidal circulating air inlet for admission of circulating air to the evaporator blocks. In order to render the discharge of exhausted air from the condenser part more favorable in the flow direction, without impairing admission of air to the evaporator blocks, and in order to expand the capacity of the expansion space, the trough-shaped housing part has a reinforcing crease at the bottom which extends longitudinally.
The evaporator blocks have a shorter length than the condenser block such that the condenser block, at its inlet side, protrudes beyond the evaporator blocks and, preferably, this area is wedge-shaped in order to enhance the dynamic pressure for support of the condenser part and to, furthermore, avoid additional wind noise.
A preferred arrangement of the condenser blowers at the discharge side of the condenser enables, depending upon the intended use of the air conditioning system, blowers to be selected to assure reliable operation of the system, while keeping the dimensions thereof as small as possible.
The evaporator blowers have a horizontally disposed axis, i.e., parallel to the evaporator blocks and in a longitudinal direction thereto. This arrangement permits a space-saving accommodation of the evaporator blowers in the evaporator part with a resultant design width of the air conditioning system.
These and further objects, features and advantages of the present invention will become more obvious from the following description when taken in connection with the accompanying drawings which show, for purposes of illustration only, several embodiments in accordance with the present invention.